This invention relates to a curtain wall system for multi-story buildings and, more particularly, to a wall system that is resistant to damage caused by swaying motions of buildings during an earthquake.
Curtain wall systems are exterior wall systems on multi-story buildings that are made of appropriate cladding materials (e.g., glass, aluminum, stone, concrete, etc.) and which carry no superimposed vertical (gravity) loads. Hence, the term xe2x80x9ccurtainxe2x80x9d implies that a curtain wall system is essentially xe2x80x9chung like a curtainxe2x80x9d from the primary structural frame of the building. A curtain wall system does not, by itself, help a building stand erect.
Although curtain wall systems are normally considered to be xe2x80x9cnon-structuralxe2x80x9d parts of a building, such terminology is misleading because curtain walls must have the ability to withstand structural loads imposed by natural phenomena such as earthquakes and severe windstorms. In this context, the term xe2x80x9ccurtain wallxe2x80x9d is a misnomer because non-structural parts of a building can be subjected to structural loads. This invention focuses on a curtain wall system that is highly resistant to the potentially damaging effects of earthquake-induced movements of building frames.
Many curtain wall systems are constructed with glass window elements glazed within an assemblage of aluminum framing members. Architectural glass, due to its brittle nature, is inherently vulnerable to curtain wall movements during earthquakes. Research studies have been conducted to investigate the seismic performance of various types of architectural glass elements held within various aluminum curtain wall framing systems using various glazing systems. Among the findings of these studies were the following: (1) architectural glass is vulnerable to damage and fallout under simulated earthquake conditions; (2) horizontal, in-plane racking movements of a curtain wall frame constitute the primary cause of glass damage and glass fallout under simulated earthquake conditions; (3) different types of architectural glass exhibit different degrees of resistance to glass fallout under simulated seismic conditions; and (4) flexural stiffness of aluminum framing members has an influence on the susceptibility of architectural glass to seismic damage (i.e., under simulated seismic conditions, stiffer curtain wall frames are associated with more glass damage and glass fallout than are more flexible frames).
Architectural glass is not the only type of curtain wall element that is vulnerable to fracture and fallout under earthquake conditions. Curtain wall systems comprised of any rigid, brittle elements such as stone panels, cementitious panels, etc. are also potentially vulnerable to the damaging effects of earthquake-induced building motions.
The primary factors causing earthquake-induced damage of conventional curtain wall systems are: (1) movements of the building""s primary structural frame in response to earthquake ground movements; and (2) the fact that vertical framing members (mullions) in conventional curtain wall systems are connected structurally to more than one floor of the primary structural frame.
The present invention is directed to solving one or more of the problems discussed above in a novel and simple manner.
In accordance with the invention there is provided a curtain wall system in which curtain frame panels of each floor are not fixedly connected to curtain wall panels of adjacent floors.
Broadly, there is disclosed herein an earthquake-immune exterior wall system for use with a multi-story building structure. The wall system includes a plurality of anchor means for connecting the wall system to the building structure, each anchor means adapted to being fixedly connected to the building structure for a single story of the multi-story building structure. Connecting means are provided for connecting each of a plurality of first elongate members directly to only one of the anchor means so that each first elongate member is fixedly connected to a single story of the multi-story building structure. A plurality of second elongate members are connected between adjacent pairs of first elongate members. The first and second elongate members collectively define panel hanging areas. A plurality of exterior cladding panels are secured to the first and second elongate members at the panel hanging areas to define the exterior wall system of the building structure.
It is a feature of the invention that the anchor means comprises steel anchor frames. Each anchor frame is rectangular in configuration and is constructed of tubular steel. The connecting means comprises anchor brackets connecting each first elongate member to upper and lower horizontal members of the anchor frames.
It is another feature of the invention that the first elongate members comprise vertical mullions.
It is an additional feature of the invention that the second elongate members comprise horizontal mullions.
It is yet another feature of the invention to provide flexible means for connecting the first and second elongate members connected to any one story to first and second elongate members connected to the story immediately above the one story. The flexible means comprises a flexible gasket of polymeric material.
There is disclosed in accordance with a further aspect of the invention an earthquake-immune curtain wall system for use with a multi-story building structure. The wall system comprises a plurality of anchor means for connecting the wall system to the building structure. Each said anchor means is adapted to being fixedly connected to the building structure for a single story of the multi-story building structure. Connecting means connect each of a plurality of vertical mullions directly to only one of the anchor means so that each vertical mullion is fixedly connected to a single story of the multi-story building structure. A plurality of horizontal mullions are connected between adjacent pairs of vertical mullions. The vertical and horizontal mullions collectively define panel frames for each story. A plurality of exterior cladding panels are secured to the vertical and horizontal mullions at the panel frames to define the exterior curtain wall system of the building structure.
It is a feature of the invention that each panel frame further includes intermediate horizontal mullions to define plural subframes and an exterior cladding panel is secured at each subframe.
This invention relates to a curtain wall system for multi-story buildings that is highly resistant to the damage caused by multidirectional swaying motions in building frames during an earthquake. In a conventional curtain wall system, each story is connected structurally to the stories above and/or below it. Interstory relative movements resulting from earthquake-induced swaying motions of the building frame cause significant load transfer from story to story and cause such a conventional curtain wall system to be susceptible to earthquake damage. Not only does this damage necessitate expensive repairs, but serious threats to life safety are imposed when debris falls from a damaged wall system. In contrast, each story of the newly invented earthquake-immune curtain wall system is structurally isolated (i.e., decoupled) from adjacent stores, which produces the beneficial effects of minimizing wall system damage and the attendant risks of falling debris (in the forms of broken glass, stone, concrete, etc.) during an earthquake.
The earthquake-immune curtain wall system achieves structural isolation of each story by employing a newly developed xe2x80x9cseismic decoupler jointxe2x80x9d between each story and a newly developed structural support system for vertical mullions in the wall system frame. As a result, relative movements between adjacent stories in the building frame transfer no significant forces between adjacent stores in the curtain wall frame. This invention embodies a curtain wall system that is essentially xe2x80x9cimmunexe2x80x9d from the effects of earthquake-induced building frame motions.